Field calculation with if statement - adding multiple fields

I'm attempting to create a custom calculation script with an if statement, a check box, and other fields to be added.

My current code is below below: 

var cTX_CHKBOX = this.getField("TX_CHKBOX").value;
var nTOTAL_PREMIUM = this.getField("TOTAL_PREMIUM").value;
var nOUR_PREMIUM = this.getField("OUR_PREMIUM").value;
var nTOTAL_PREMIUM_UCC = this.getField("TOTAL_PREMIUM_UCC").value;
var nOUR_PREMIUM_UCC = this.getField("OUR_PREMIUM_UCC").value;
var nESCROW_FEE = this.getField("ESCROW_FEE").value;
var nCPL_FEE = this.getField("CPL_FEE").value;
var nFEDEX_FEE = this.getField("FEDEX_FEE").value;
var nSEARCH_FEE = this.getField("SEARCH_FEE").value;
var nRECD_FEE = this.getField("RECD_FEE").value;
var nTRANSFER_TAX = this.getField("TRANSFER_TAX").value;
var nTIEFF_FEE = this.getField("TIEFF_FEE").value;
var nMISC_CHARGE_FEE_I = this.getField("MISC_CHARGE_FEE_I").value;
var nMISC_CHARGE_FEE_II = this.getField("MISC_CHARGE_FEE_II").value;
var nADDL_FEE = this.getField("ADDL_FEE").value;
if ( cTX_CHKBOX == "Off" ) event.value = nOUR_PREMIUM + nOUR_PREMIUM_UCC + nESCROW_FEE + nCPL_FEE + nFEDEX_FEE + nSEARCH_FEE + nRECD_FEE + nTRANSFER_TAX + nTIEFF_FEE + nMISC_CHARGE_FEE_I + nMISC_CHARGE_FEE_II + nADDL_FEE;
else event.value = nTOTAL_PREMIUM + nTOTAL_PREMIUM_UCC + nESCROW_FEE + nCPL_FEE + nFEDEX_FEE + nSEARCH_FEE + nRECD_FEE + nTRANSFER_TAX + nTIEFF_FEE + nMISC_CHARGE_FEE_I + nMISC_CHARGE_FEE_II + nADDL_FEE;

Basically, the code works that if the box is not checked to add certain fields together, and if checked, to other certain fields together.

(note: the only fields that change between the two or nOUR_PREMIUM/nOUR_PREMIUM_UCC and nTOTAL_PREMIUM/nTOTAL_PREMIUM_UCC)

When I input this code, the calculation field does not sum at all, and stays zero regardless if the box is checked.

I've also tried the number variables with the Number(this.getField("X')value); syntax, and that didn't work either.

Thank you in advance for any help you can give!

Brett